1. Field of the Invention
The present invention relates to an electrical connecting structure preferably to be used for a cable reel contained in a steering apparatus of automobiles. More specifically, it relates to a favorable electrical connecting structure even when the number of cable wires of the flat cable contained inside a stator and a rotor, etc., which are connected to the external cable wire by bus bars, is increased.
2. Background of the Invention
In the conventional construction of the cable reel 1 contained in a steering apparatus of an automobile, as shown in FIG. 7, a stator (external cylinder member) 2 which is fixed to the side of steering column is connected in a relatively rotatable manner to a rotor (internal cylinder member) 3 which is mounted in the steering wheel (handle) to interlockingly rotate with the steering wheel. Further, a flexible flat cable 5 is contained spirally in the annular hollow 4 existing between the stator 2 and the rotor 3 so that the flat cable 5 is wound or unwound in accordance with the forward and/or reverse rotation of the rotor 3 which is operated in accordance with the wheel rotation.
The flat cable 5 is composed of conductors made of copper foil etc., which are arranged in parallel and both sides of the conductor are sandwiched by insulating resin film. Further, the flat cable is electrically connected to an external cable by means of a bus bar which is insert molded into a case for connection of the conductor. Namely, as shown in FIG. 8, one end 6a of the conductors 6 of the flat cable 5 is electrically connected to the external cable wires 53 in the body side by means of bus bar 52 inside the case 51, which is contained in the stator 2. On the other hand, the other end 6b of the conductors 6 of the flat cable 5 is electrically connected to cable wires 56 in the steering wheel side by means of bus bar 55 inside of case 54 which is contained in the rotor 3.
More specifically, as shown in FIGS. 9 and 10, the bus bars 52 and 55 are fixed by molding in the internal surface of the respective case 51 and 54. Respective ends 6a and 6b being exposed parts of the conductor 6 of the flat cable 5 are connected by welding to respective ends of the bus bar 52 and the bus bar 55. The exposed core wire end of cable wire 53 and cable wire 56 are connected by welding to the other end of the bus bar 52 and the bus bar 55. After these conductor and core wires are connected by welding, the bus bar mounting surface of each case 51 and case 54 is covered with a respective cover 57 and 58. Then, the case 51 and the case 54 are connected by assembling to the stator 2 and to the rotor 3, respectively.
In conventional electrical connecting structures, however, it is very difficult to take measures to solve the problem of the increase in the number of conductors 6 of the flat cable 5 and the external cable wires 53 and 54. Namely, electric wiring systems to be provided in an automobile steering wheel have increased nowadays, besides the trend of air bags, so that the number of circuits is increasing. With one more pair of bus bars being added to obtain two pairs of bus bars, we can double the number of circuits. However, with the aforementioned conventional structure, since the case and cover become necessary for every pair, the number of the cases and covers naturally become doubled. Thus, the cost should inevitably be tremendously increased because of the multiplication of the number of members and the assembly processes. Moreover, since the required space will also necessarily increase, it is difficult to secure further assembling space for the needed increase within the very limited space available.
This problem can occur not only in the connection of the flat cable of a cable reel to a cable wire, but also in the case of a plurality of flat cables or in the case that the number of cable wires for connection is increased by multiplying the number of conductors of one flat cable.
Accordingly, an object of the present invention is to provide an electrical connecting structure without requiring additional space and an increase in the number of members even in the case where the number of conductors of the flat cable and the number of connection circuits of the external cable wire are increased.
In order to solve the aforementioned problems, the present invention provides an electrical connecting structure for connecting conductors of a flat cable to core wires of a wire cable by bus bars. The connecting structure includes a plurality of case members, at least one strip-type bus bar fixed in parallel to the respective case member. The conductor of the flat cable is connectable, for example, by welding, to one end of the bus bar, and the core wire of the cable wire is connectable, for example, by welding to the other end of the bus bar. The plurality of case members are superposed so that a bus bar mounting surface of one of said plurality of case members is covered with the other of said plurality of case members. Furthermore, an engaging mechanism that engages the respective case members is provided on each case member, and the plurality of case members is united into a single unit by the engaging structure.
The aforementioned electrical connecting structure is appropriate for a cable reel which is fixed in a steering apparatus.
Namely, a flat cable is contained in annular hollow formed by the stator and the rotor in a cable reel. Furthermore, a bus bar is fixed inside of the case for connection which is fitted in the stator and the rotor, and the conductors of the cable reel and the core wires of external cable wires are connected to opposite ends of the respective bus bars.
The case for connection which is fitted in the stator and/or rotor is formed of several case members. The case members are superposed so that a bus bar mounting surface of one of the case members is covered with another case member. An engaging mechanism that engages the respective case members is provided on each case member, and the case members are united into a single unit by the engaging structure.
With the aforementioned structure, the number of circuits can be sufficiently increased because the plurality of case members containing bus bar fixed by molding can be provided. Moreover, since the bus bar mounting surface of each respective case member is covered by the other case member, a separate cover for covering the bus bar mounting surface will not be necessary, so that an increase in the number of members and the number of assembly processes can be limited and costs will not be greatly increased. Further, since a separate cover that covers the bus bar mounting surface is not necessary, an increase in the required space for assembly can be limited. It is also easy to arrange the case because the case is united as a single compact unit by superposing all case members by the engaging mechanism provided on each case member.
More specifically, the superposing is conducted under the condition that the bus bar mounting surface of a lower case member faces upwardly, and, on the other hand, the bus bar mounting surface of an upper case member faces downwardly.
In addition, a flat cable insertion groove is provided on one side of the aforementioned case members, and cable wire insertion grooves are provided on the other side of the aforementioned case members. Since the case members are superposed on each other, the cable wire insertion grooves of both the upper case member and the lower case member are superposed and connected to each other, so that the cable wire grooves in the upper case member directly overly the cable wire grooves in the lower case member so that cable wires mounted in the upper case member directly overly cables wires mounted in the lower case member. Alternatively, the cable wire grooves in the upper case member are staggered with respect to the cable wire grooves in the lower case member, so that the cable wires mounted in the upper case member are staggered with respect to cable wires mounted in the lower case member.
In another aspect of the present invention, the aforementioned case member is superposed with the bus bar mounting surface facing upwardly in order to cover the upper surface of the uppermost case member by a cover.
In this case, even when the number of case members is two or more, a single cover (covering member) is sufficient, so that the number of members can be reduced and the space required can be limited.
The case made up of the aforementioned plurality of case members can be provided in both sides, which means the connection side of the conductors of the flat cable and the cable wires of the body side, and the connection side of the conductors of the flat cable and the cable wire of wheel (handle) side, or the case members can be provided in either side.
Further, the connection of the aforementioned bus bars and the conductors of the flat cable, and the connection of the bus bars and the core wires of the cable wire may be conducted by ultrasonic welding or resistance (spot) welding methods.